Since periodontal disease seems to recur after 3 - 4 years, we have suggested a 5 year follow-up-study. Blinding I: To the Project Leader who is the one who performs all measurements, the randomization to groups will be hidden since it is the research Coordinator (N) who does this. N will also keep track of time schedules, appointments etc. A separate record with the patient names and study number (1 - 160) will be kept by N locked down in a separate cabinet for such patient records. At measuring appointments the measurements are sent by N to the code book master who will log all measurements into SPSS program for statistical evaluation.